The South African government has decided to send more troops and military weapons to fight the anti-government armed group M23 in the east of the Democratic Republic of Congo (DRC).

The move comes days after South Africa accused Rwanda - which supports M23 - of killing 14 of its soldiers.

The South African reinforcement comes amid fears that the fighting in eastern Congo could trigger a wider war in a powder-keg region that has witnessed genocides, cross-border conflicts and dozens of uprisings over the past three decades.

The 800 or so soldiers left for the Lubumbashi region in southern Congo last week. A local airport source confirmed to Reuters that he had seen old planes from South Africa land.

"We have been informed of a build-up of [South African National Defense Force (SANDF)] troops in the Lubumbashi area. We gather that about 700-800 troops have been flown into Lubumbashi," Chris Hattingh, the DA's defense spokesman, told Reuters.

However, another South African defense source said he was unaware of the issue, and the same was true of Congo's counterpart.

Lubumbashi is about 1,500 km south of Goma, the eastern town on the border with Rwanda that the M23 rebels took last month during an offensive that killed more than 2,000 people and displaced hundreds of thousands.

South Africa is believed to have around 3,000 troops deployed in the DRC, both as part of a UN peacekeeping mission and as a southern African regional force tasked with helping the DRC army fight the M23 insurgency.